Apparently the Post Office police maintain their own secret spy budget. Fox News' Denver affiliate reports on what happened after a customer at a Denver post office noticed a strange looking utility box, and the journalists looked into it:
Within an hour of FOX31 Denver discovering a hidden camera, which was positioned to capture and record the license plates and facial features of customers leaving a Golden Post Office, the device was ripped from the ground and disappeared.
FOX31 Denver investigative reporter Chris Halsne confirmed the hidden camera and recorder is owned and operated by the United State Postal Inspection Service, the law enforcement branch of the U.S. Postal Service.
The recording device appeared to be tripped by any vehicle leaving the property on Johnson Road, but the lens was not positioned to capture images of the front door, employee entrance, or loading dock areas of the post office.
According to Fox Denver, the managers of the post office in question denied knowledge of the device. While a federal postal police employee told the reporters that its officials "do not engage in routine or random surveillance," and only use deploy cameras for "law enforcement or security purposes" or criminal investigations, the journalists were unable to find any criminal warrant applications describing the placement of a face recognition and license plate tracking camera in Denver.
After filing "multiple Freedom of Information Act requests with the Postal Service, Postal Inspection Service, and Office of the Inspector General," reporters found that these agencies apparently maintain no written policies to govern how and why cameras like this one might be deployed, or the data from them used.
In July 2013, the New York Times revealed the existence of a possibly unconstitutional 'mail covers' program at the Postal Service. A 2014 Inspector General report showed that the US Postal Service received nearly 50,000 law enforcement requests to monitor mail in 2013. The ACLU's Jameel Jaffer told Newshour that this warrantless surveillance was "yet another reminder" that there aren't enough rules limiting snooping powers, and that those that exist are insufficiently enforced. “When a targeted surveillance tool is used on this scale, the distinction between targeted and dragnet surveillance begins to seem academic," he said.